The present invention relates generally to a method and apparatus for removing contaminants from groundwater, and, more particularly to an in-situ air stripping, oxidation, and adsorption method for removing volatile organic compounds (VOCs) from groundwater.
Contamination of the phreatic zone, also known as zone of saturation, or, groundwater, with potentially hazardous materials is a common problem facing industry, the government and the general public. The most common type of VOC pollutants are petroleum based products and chlorinated solvents. Frequently, as a result of spills, leakage from storage facilities or surface discharges, contaminants percolate into groundwater, thereby posing a threat to drinking water supplies.
While groundwater is not as susceptible to pollution as surface water, once polluted, its restoration is difficult and long term. Typically, contaminated groundwater is removed from the phreatic zone, treated and discharged or returned to the phreatic zone. These "pump-and-treat", or above ground, methods, are relatively expensive. There have been some recent developments in insitu water treatment which employ air lift pumping as a means of producing gas bubbles to remove VOCs. The theory of these known methods is that gas is pumped into the wells which causes water and subsequently formed gas bubbles to rise upward. VOCs are transferred from the contaminated water to the gas bubbles which can then be collected for treatment. However, frequently these devices do not result in rapid mass transfer and vapor saturation which results in a slower and less efficient process. Vapor saturation occurs when the rising bubbles become saturated with VOC vapor. Therefore, there is a need for the development of an insitu air stripping, oxidation, and adsorption remediation method for removing contaminants in a relatively inexpensive and more efficient manner.
The present invention involves new concepts for in-well removal of contaminants from the saturation zone. It avoids expensive "above ground" remediation methods, and provides a more efficient method of mass removal of dissolved contaminants. The present invention combines packing/stripping materials (balls) with air stripping techniques in the well. In addition oxidation and adsorption techniques can also be incorporated to compliment the air stripping effect to achieve higher mass removal efficiencies. The injected gas may be air or any specific or combination of gases such as nitrogen gas. The injected gas can be at any desired temperature.